/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.library.frequency;

import org.apache.iotdb.library.frequency.util.FFTUtil;
import org.apache.iotdb.library.util.Util;
import org.apache.iotdb.udf.api.UDTF;
import org.apache.iotdb.udf.api.access.Row;
import org.apache.iotdb.udf.api.collector.PointCollector;
import org.apache.iotdb.udf.api.customizer.config.UDTFConfigurations;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameterValidator;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameters;
import org.apache.iotdb.udf.api.customizer.strategy.RowByRowAccessStrategy;
import org.apache.iotdb.udf.api.type.Type;
import org.eclipse.collections.impl.list.mutable.primitive.DoubleArrayList;
import org.jtransforms.fft.DoubleFFT_1D;

/**
 * This function does Fast Fourier Transform for input series.
 */
public class UDTFFFT implements UDTF {

    private boolean compressed;
    private FFTUtil fftutil;
    private final DoubleArrayList list = new DoubleArrayList();

    @Override
    public void validate(UDFParameterValidator validator) throws Exception {
        validator
                .validateInputSeriesNumber(1)
                .validateInputSeriesDataType(0, Type.DOUBLE, Type.FLOAT, Type.INT32, Type.INT64)
                .validate(
                        x ->
                                ((String) x).equalsIgnoreCase("uniform")
                                        || ((String) x).equalsIgnoreCase("nonuniform"),
                        "Type should be 'uniform' or 'nonuniform'.",
                        validator.getParameters().getStringOrDefault("method", "uniform"))
                .validate(
                        x ->
                                "real".equalsIgnoreCase((String) x)
                                        || "imag".equalsIgnoreCase((String) x)
                                        || "abs".equalsIgnoreCase((String) x)
                                        || "angle".equalsIgnoreCase((String) x),
                        "Result should be 'real', 'imag', 'abs' or 'angle'.",
                        validator.getParameters().getStringOrDefault("result", "abs"))
                .validate(
                        x -> (double) x > 0 && (double) x <= 1,
                        "Compress should be within (0,1].",
                        validator.getParameters().getDoubleOrDefault("compress", 1));
    }

    @Override
    public void beforeStart(UDFParameters parameters, UDTFConfigurations configurations)
            throws Exception {
        configurations.setAccessStrategy(new RowByRowAccessStrategy()).setOutputDataType(Type.DOUBLE);
        String result = parameters.getStringOrDefault("result", "abs");
        this.compressed = parameters.hasAttribute("compress");
        double compressRate = parameters.getDoubleOrDefault("compress", 1);
        this.fftutil = new FFTUtil(result, compressRate);
    }

    @Override
    public void transform(Row row, PointCollector collector) throws Exception {
        double v = Util.getValueAsDouble(row);
        if (Double.isFinite(v)) {
            list.add(v);
        }
    }

    @Override
    public void terminate(PointCollector collector) throws Exception {
        int n = list.size();
        DoubleFFT_1D fft = new DoubleFFT_1D(n);
        // each data point count for 2 double values (re and im)
        double[] a = new double[2 * n];
        for (int i = 0; i < n; i++) {
            a[2 * i] = list.get(i);
            a[2 * i + 1] = 0;
        }
        fft.complexForward(a);
        if (compressed) {
            fftutil.outputCompressed(collector, a);
        } else {
            fftutil.outputUncompressed(collector, a);
        }
    }
}
